Current investigations involve examining the utility of intracranial self stimulation (ICSS) as a viable technique for studying the positively reinforcing component of opiate central activity. Experiments are designed to determine (1) the ability of opiates to modify ICSS in dose-responsive manner, (2) the stereoslectivity of opiate-induced changes in ICSS, (3) the influence of specific narcotic antagonists on opiate-induced changes in ICSS, (4) the development of tolerance to the positive reinforcement component of narcotic action, (5) the neurochemical basis for the influence of opiates on central reward systems and (6) the ability of endorphins to modulate ICSS. The information generated in used to enhance our understanding of the molecular mechanisms responsible for the phenomenon of opiate tolerance and dependence.